22 Prof. M uller on the Development 



136. Neriene saxatilis. 



Neriene saxatilis, Blackw. Annals and Mag. of Nat. Hist. vol. xiii. 

 p. 183. 



A male of this Neriene, having the palpal organs fully deve- 

 loped, was discovered among loose fragments of rock in a wood 

 at Hendre House, near Llanrwst, in June 1841. 



137. Neriene avida. 



Neriene avida, Blackw. Annals and Mag. Nat. Hist. vol. xiii. p. 185. 



Males and females of this spider were found on rails at Oak- 

 land in April 1839. 



138. Neriene timida. 



Neriene timida, Blackw. Annals and Mag. Nat. Hist. vol. xiii. p. 183. 

 Both sexes of this species were taken on rails at Oakland in 

 April 1841. 



139. Neriene flavipes. 



Neriene flavipes, Blackw. Annals and Mag. of Nat. Hist. vol. xiii. 

 p. 182. 

 In February 1841 adult males of Neriene flavipes were cap- 

 tured on rails at Oakland. 



140. Neriene parva. 



Neriene parva, Blackw. Linn. Trans, vol. xviii. p. 647. 



Argus minimus, Walck. Hist. Nat. des Insect. Apt. t. iv. p. 512. 



Specimens of this very minute spider were detected on rails at 

 Oakland in January 1837 ; they were all males, and had the pal- 

 pal organs perfectly developed. 



IV. — Upon the Development of Mollusks in Holothurise. 

 By Prof. Muller*. 



In the Bay of Muggia, at Trieste, a Holothuria of the genus 

 Synapta is very abundant. It was first discovered by Montague 

 upon the English coast, and was by him called the Holothuria 

 digitata, and so much of its anatomy as could be made out 

 from specimens preserved in spirits has been set forth in the 

 ' Anatomische Studien iiber die Echinodermenj".' In the living 

 Synapta digitata I first discovered those suckers upon the ten- 

 tacles, which Quatrefages had described in another Synapta, and 

 some other anatomical peculiarities not observed by that writer, 



* Read before the Royal Academy of Sciences of Berlin, Oct. 16, 185L 

 t Muller's Archiv, 1850, 



